Subchronic toxicity of 3,3',4,4'-tetrachlorobiphenyl in the rat liver: an electron microscope study.

Ultrastructural effects of 3,3'4,4'-tetrachlorobiphenyl (PCB) congener #77 on the liver were evaluated following its feeding to Sprague-Dawley weanling rats. Treatment diets were prepared by dissolving the congener in 4% corn oil. Ten animals, either male or female, in each group were placed on the respective diets containing 10, 100, 1,000 and 10,000 ppb congener for 13 weeks. Ten animals of each sex served as the control that had only the oil added to the diets. In the congener-exposed animals the alterations consisted of a marked increase in the profiles of smooth endoplasmic reticulum, and in the heightened number of lipid droplets in many parenchymal cells. Several mitochondria showed abnormalities such as dumbbell shapes, and in others, the cristae were oriented parallel to the long axis of the organelle. Peroxisomes were numerous in the 10 ppb group and apparently had increased numerically in the liver of animals from the higher dose groups. Females were notably more affected by the congener when compared to their male counterparts. The results indicated that the compound is mildly toxic, and alteration in structure and function can be noted at the lowest dose used (10 ppb congener exposure). It is concluded that congener #77 may be moderately toxic and it may affect the overall health of the exposed animal.